Television pickup control system



Aug. 21, 1945. G. l.. BEERS TELEVISION PICK-UP CONTROL SYSTEM Filed-July'l. 1943 '2 Sheets-Sheet l Mmm/EY -fier without the PatentedAu 2l, 1945 George L. neen, maaennelafn. J., einer se Radio Corporation of America, la corporation ot Delaware Application July 31, 1,943, Serial No. 496,905

Claims.

The present inventionrelates to av television pickup control system, and more particularly to a novel arrangement for obtaining a maximum amount of useful signal in the output of television pickup equipment under varying light conditions.

,Certain dimculties are encountered in television pickupwork because of the variation in illumination ofthe scene to be televised. vWith the usual television camera a camera operator cannot adjust the size oi the stop or iris opening and fulll his other obligations. If the iris adjustment control is made accessible to the operator when he is at his normal stationv in back of the camera, then it is possible for him to adjust the size of the aperture, but some indication of relative light intensity must be provided and such a device, ii.' it gives a true indication of the eil'ective illumination ot the scene upon which the camera is trained, is complicated and expensive. The camera view iinder cannot be relied upon for indicating the degree and quality`4 of illumination on the scene which is being televised, since it is tee dimeult te interpret the image in the view ilnder in terms vci factors affect the signal which is generated in and transmitted from the television camera, in-

cluding changes in ampliiler conditions, such as changing biasing and supply voltagesof which the camera operator can have no knowledge. In the case of television programs which originate outdoors, such as sporting events, it is necessary that the cameraman give his individual attention to the rscene in the viewilnder.

In a typical television pickup system there are two adjustable means vfor controllingthe overl 4all sensitivity of the system. One of these is the gaincontrol on the video frequency ampliiler and the-other is the aperture control on the television camera lens. lThe sensitivity` of the system cannot be increased beyond a certain point by increasing the gain oi the video ampli-` i introduction off objectionable noisein the reproduced picture.' 0n thev'other han'd. the maximum sensitivity'which cani-be obtained by increasing the aperture of the`l is in many instances limited by the Idepth of focus which is obtained under thev wide aperture condition.'

. vUnder adverse lighting conditions it may-benecessary to operate a-television pickup sys'l tem with the camera lens at its maximum aperture and the video frequency amplifier adjusted for high sain. It under these conditions the'ts (ci. 17e-7.2i

light 'intensity should increase and a corre-e spending reduction in the over all sensitivity of the pickup system is desired, this decrease in sensitivity can be obtained either by reduction 5 of the gain in the video amplifier or by a change in the iris diaphragm setting for the` camera lens.

It is therefore apparent that in a television pickup system there are two independent controls .for determining the4 over all sensitivity of the system. These are normally operated by `diiferent individuals, and under conditions where sudden and frequent variations in illumination may occur, as in outdoor Lpickup work, a certain amount of confusion may result through theV fuse of these independent controls.

i In orderv to obtain the maximum in performance from such a system,\'it is desirable, as the light intensity increases on the `subject being televised, to iirst reduce the gain oi the video frequency amplifier tothe point where amplier noise is not apparent in the reproduced picture and then to obtain any further reduction in sensitivity corresponding to a vfurther increase in light by decreasing the lens aperture so that the' the generatedA camera signal. Moreover, other depth of focus is correspondingly increased. This coordinated control oi' video gain and aperture-setting cannot be obtained satisfactorily when'two individuals are responsible for the setting of these two controls.

In accordance with the. present invention means are provided to enable the operator at a monitoringvcontrol station to exercise coordinated controliof the ampliiler gain, taking into account all of the factors adecting the generated 4Q a faithful image ot the televised scene. It will be apparent to those skilled in the art that when a television signal pickup and transmitting system embodving the invention is employed in l televisinga scene or object --in a television studio.

`the'lightin'g arrangement may be simpliiied or the lighting of the scene may be changed to obtain specialfeiiects, and the'continuity of the program need not be interrupted for the pur# pose of making camera iris or gain control ad- 'I'he principal object of the invention. therefore, is to provide means for obtaining a 8emcrated and transmitted signal from a television camera whichmay be employed in the reproduction oi an inage o! the televised scene having maximum foreground and background detail consistent with a satisfactory freedom from noise.

vprovide a combined camera aperture and signal gain control in a television system.

Still another object of the invention is to provide an adjustable control mechanism for the combined control of the aperture of a television camera and the gain control vmeans of a tele- K' vision system in which the camera is employed.

Still further objects of the invention will become apparent and suggest themselves to those skilled in the art to which the invention is directed upon reading the following specification and claims in connection with the drawings in which: y

Fig. 1 is a schematic showing of a television pickup system, including a camera and the related output monitoring console.

Fig. 2 is a detailed sectional view sectioned on line 2 2 of Fig. 3 showing one arrangement in accordance with the invention for operating certain of the controlsshown in Fig. 1.

Fig. 3 is a plan view in section on line 3-9 of Fig. 2 of the mechanisml of Fig. 2.

Fig. 4 is a view in plan of the control knob of F18. 1.

The pickup system selected for purposes of illustration is more or less conventional and comprises a camera 9 housing a pickup tube IIi, shown as being of the storage type containing a light sensitive mosaic II and the usual auxiliary electrodes and electron emitters. These electrodes include the anode and cathode for producing the cathode ray beams. The cathode ray beam deflecting means or yoke is indicated conventionally at I2 and may, comprise horizontal and vertical defiecting coils for producing a scanning movement of the beam which is directed on the mosaic II to release a signal output therefrom to a load circuit. The released signal output of the pickup tube III is applied to a preamplifier I4 across a load resistor I 9 in most conventional devices. After initial amplification, the signal is transmitted to a video signal amplifier combination which is represented schematically at I6. .Reference numeral I1 indicates a synchronizing signal generator of conventional form which generates suitable synchronizing and blanking signals, in known manner, and which lmonitor tube 99 and an oscilloscope 4I.

- control 29.

aasaaes 1 of focus when the televised scene is well illuminated. Reference character 24 indicates a bevel gear, which is secured to or otherwise operatively associated with the rotatable collar which adjusts the degree of opening of the iris diaphragm. The rotatable shaft 21 of the receiver 29 of a Selsyn motor system carries a bevel pinion 9| meshing with the bevel gear 24 and by this arrangement, when the shaft 21 is rotated, adjustment of the iris diaphragm will be obtained. The

Selsyn motor system is shown as being the ordinary cascade arrangement of polyphase alternating current motors, the stators of which are connected to a polyphase alternating current supply` source 92. Any Selsyn .or equivalent system may be used. It will be understood that any other arrangement for converting motion produced at the Selsyn motor system receiver 29 into changes in the iris diaphragm opening or equivalent lens stopping means may be employed.

The movable member (not shown) of the transmitter 99 of the Belsyn motor system is provided with an operating knob 94. A gain control 36 for the amplifier I6 is provided with a suitable knob or manual control 91, and the operating knob 94 of the Selsyn motor transmitter and the knob 91 are preferably positioned so as to be conveniently accessible to a control operator stationed within viewing distance of a picture The monitor tube 99 is shown as being connected through a monitor amplifier 42 to the video signal amplifier IB. The oscilloscope 4I is also connected to this amplifier and toI an oscillator 40 which generates a saw tooth wave or a wave of any suitable shape for expanding'the video signal or portions thereof along a coordinate axis into an observable trace in the `usual manner. The oscillator 49 may be controlled from the synchronization signal generator as shown.

In operation of the arrangement just described.' the camera operator need only focus the camera on .the scene to be 4televised by ,manipulating the At this time the operator at the los -cation of the controls 94 and 91 will open the`iris is shown as being connected to the ray defiecting means I2 by Way of conductors 25 and 2B to supplythe horizontal and vertical beam deilection v energy and by conductor 29 to the, control electrode member of the electron gun (not shown) of the scanning tube I9 to provide the return line blanking. The same general types of signals are falso supplied to an output amplifier I8, usually referred to as a line amplifier, by way of .conductor 95. The resulting composite synchronizing and picture signal output of the amplifier I8 may be transmitted over any suitable transmission channel to a distribution point such as a radio transmitter. The camera 9 is equipped in the usual manne with a lens combination I9 suitablefor imaging the scene to b televised on the mosaic Il. A

diaphragm so as to obtain the largest aperture vor stop ,size of the lens combination I9. He will then manipulate the knob 91 of the gain control 99 so as to obtain an optimum signal to noise ratio, thereby providing maximum gain for the given illumination and noise conditions. The operator in doing thi will be guided by the signal trace appearing i the oscilloscope 4I and the picture imagewhich is reproduced by the monitor tube 99. This setting of the gain control will be maintained and the knob 94 may be rotated in the direction* of the arrow to obtain maximum depth of focus by stopping down 4the lens combination I9. An indication of the smallest aperture which can be used effectively will be given by the monitor tube 99 and the oscilloscope 4I as before. The system may be operated in such a manner that -there is some overlap in the func- Referring to Figs. 2, 3, and 4 of the drawings.

. disc 92, the periphery an arrangement is shown whereby a gaincontrol resistance unit or potentiometer 49 and a remote control transmitter 44 can be operated from a single manually operable control handle or knob 49. 'The-potentiometer and the transmitter 44 may, for example, be similar to the gain control l1 and the Selsyn transmitter 39 of Fig. 1 of the drawings. However, it will be understood that any two controls of a remote control system. may be operated by the mechanism presently to be described in detail.

'I'he knob 49 is secured at the end of the operating shaft 41 of the resistance unit or potentiometer, The potentiometer 43 is secured, as by a sheet of insulation 49, or in any other suitable manner, within a housing 52 which is shown fragmentarily on Fig. 2 of the drawings and in planin Fig. 3. The top of this housing is pro-` vided with a boss Il which is apertured to form a bearing for the shaft 41. The Selsyn transmitter' 44 is also secured within the housing 92 and is provided with terminals 59 for connection with a suitable 4polyphase alternating current source. The transmitting terminals 09 of the transmitter are available for connection to a Selsyn receiver such as the receiver 29 of Fig. 1 of the drawings.

Driving connection from the shaft 41 to the drive shaftl 9| of the Selsyn transmitter is obtained through the medium o1- a friction drive tionally engaged by a shoe member 99 of any desired friction material such as leather, a plastic,l

or the like. The friction discV 92 isl secured as by rivets 99 to a gear i9 which isA rotatably mounted on the boss 59. Preferably, the `friction disc 92 is also rotatably mounted on the boss 53. The gear 99 meshes with and drives a pinion 1| secured to the Selsyn transmitter drive shaft 9|. Shaft 9| may be geared down to give approximately one turn of the Selsyn rotor for one turn of the indicator if desired, or the gear S9 and pinion 1| may be interchanged.

Frictional engagement of the shoe 99 with the friction disc 92 is controlled by the cam surface 12 of a ring 19 whichis slotted at angularly spaced points as indicated by reference character 14 to accommodate clamping screws 16 threadedly engaged in the housing 92. The slots l: provide for angular adjustment of the ring 'l screws 19 around the top o f the casing 52 and by elongating the' slots 14. The cam surface 12 is oifset asfindicated at 11 to reciprocate a cam follower 19 .adjustably secured, as by a set screw 90 (Fig. 3). upon a reciprocable'rod 92 biased to the right as viewed in Fig. 2 by a compression spring 9|. The rod 92 is slidably. carried by tangs 99 formed on, or integral with, a pointer or an indicator 99 which is secured directly to the shaft41 or to a ring 90 which may be keyed or sweated on the shaft 41. The end 91 of the indi- 99 of which is to be fricf 99.7which is secured to the shaft 41, will turn and by reason of frictional engagement of the shoe 99 with the friction disc 92, the gear 99 will be rotated causing the Selsyn transmitter shaft 9| to be rotated. concurrently with this, the potentiometer 49 is adjusted. 'Ihe shaft 41 will continue to drive the gear 99 in the manner just described until a raised portion in the cam track such as the offset" is reached, whereupon the rod 92 will be moved toward the left by the cam follower 19 to cause disengagement of the shoe 99 from the friction disc 92. This point of disengagement, which is also'the point of engagement when the knob 49 is turned in a clockwise direction to decrease the gain, may be chosen so that when the gain is decreased to a given point, the iris diaphragm control will be operated along with the potentiometer". 'I'he slots 14 in conjunction with the set screws 19 permit selection of the point of engagement of the Selsyn drive.

In order to provide for conveniently releasingl the Selsyn transmitter drive at any time, irrespective of the cam track 12 so that the potentiometer '49 may be separately adjusted, a member 92 is pivotally mounted at y)99 in a slot 99. in the knob 49. A compression spring 99 may be provided to keep the member-,92 in its inoperative position when it is not deliberately grasped by the hand of an operator when rotating the knob 49. An extension lill on the member 92 extends downwardly to engage a stop member |02 adjustably secured, as by a set screw |09 (Fig. 3), on the rod 92.

When the knob 49 is turned with the -member 92 pressed inwardly, it will be seen that the rod 92 will be moved to the left, releasing the shoe l 99 from engagement with the friction-disc 92.

A complete range of adjustment may be provided by locating several sets of holes for the The disc 62 is provided with graduations |04 (Fig. 3), and a stationary disc |09 is provided with a vscale of g'raduationsl |01.v The stationary disc |09 is secured in any suitable nanner, as by a set screw |09, to the upper portion of the boss 53 which projects beyond the disc 92.

The indicator 86 is provided with an aperture ||0 which is covered by a window of suitable transparent material, such as glass or a transparent plastic, secured in any suitable manner to the indicator. A cross hair H3 is provided on the window so that it will cooperate with the scales |04 and |01 of the friction disc G2 and the stationary disc |09, respectively.

The cam ring 19 is provided with graduations ||4 which cooperate with a mark H9 on the housing 52 to assist in adiustingthe'ring 13 angularly with respect to the top of the housing 52 so that the desired point of engagement and disengagement of the shoe 99 with` the periphery 99 of the friction disc 92 may be oriented with Y respect to any point on the stationary scale |01.

cator 99 is turned at lan angle to its main porscrew 9|'v (Fig. 3)-, to the rod 92.

From the parts thus far described, it will bev seen that as the knob 49 is turned, the indicator Briefly, the combined control mechanism of Figs. 2 to 4 in the drawings is operated in the following manner.

When the knob 49 is manipulated to move the indicator 99 in a clockwise direction as viewed in Fig. 3;.the gain of the ampiiiler controlled by potentiometer- 49 is reduced. The maximum gain setting may beindicated by thev letter M on the scale |01 as shown. The mechanism is arranged so that rotation of the disc 92 in a clockwise direction reduces the aperture of the lens of the associated television camera,- for example, by anl arrangement vsimilar to that shown in Fig. 1 of the drawings.

The angular position of the disc B2 which corresponds to the maximum opening of the camera iris may be `indicated by` a or other suitable mark on the scale |01 coming into register with any desired indicating mark onthe stationary disk |06. If theI mark M on the scale |01 is chosen, the O and M will be in about the relative positions shown on Fig. 3 after turning the indicator to the position shown, since the odiset 11 will have caused the disc $2 to be displaced clockwise angularly by approximately the amount shown. -The relative position 'of the parts shown by Fig. 3 is to be taken as illus- Y trative only and not as showing an absolute mode of operation. i

Under typical operating conditions of a television system, the cam ring` 13 is locked by the screws 16 in an angular position such that the cam offset 11 is effective when the indicator 88 is turned` clockwise to the point' where the noise level may be tolerated. f

It will be understood that lighting conditions on the scene to be televised will govern the setting of the adjustable parts of the combined mechanism disclosed herein so that only a generai outline of the mode of operation can be given. Those skilled in the art, to which this disclosure is addressed, will be able to operate 'the mechanism Kprovided by this invention in such a manner as to obtain best results under varying conditions oi lighting on the scene to be televised and varying noise conditions which are present in the electrical portion of the television system.

For example, under a given light condition, the disc 62 may be set initially to the point corresponding to the iuli open setting of the camera iris. The knob de will be rotated clockwise from a position near the counterclockwise end of its range of movement to reduce the video gain until noise disappears, or can just be tolerated as shown by the oscillograph or the video monitor tube, and at this point the setting of the `cam ring 13 is chosen so that the indicator 8S will engage the disc 62 through the medium of the friction shoe i8 and cause the disc to rotate with the indicator n. nom this point the camera aperture will be decreased 1 to sharpen up the detail of the picture, and the gain will be further-reduced. Gain reduction from this point may be at a decreased rate it desired, by selecting a potentiometer having a non-uniformv resistance unit.' This suggested mode of 'operation described by way. of example is suitable tor conditions where the'light is a minimumand maximum gain must be employed.

The potentiometer 4I maybe of the type which has a taperingresistance unit so that the reduction in the gain will be slight during a portion of the 'range of movement of the indicator able gain control for said amplier, a stop adjustment for said lens, remotecontrol means for said stop adjustment means located adjacent to said gain control, an oscilloscope, and means to supply said oscilloscope with signals produced by said picture scanning rtube, said remote control means and said adjustable gain control being accessible 8l,- or if desired, thel potentiometer may be so larranged that no further reduction ingain occurs after the friction shoe Il comes in contact with the cam surface Il oi" the disc' 02.'

From 'the foregoing it will bessen that.the arrangements described herein provide the maximum depth'of 'focus for 'any given light condition 'and also that Vit is not susoeptibleof in` terference` onthe `part oi.' the camera operator. these arrangements permit a convenient balancing of the noise factor against the iris under extremelyYA adverse conditions so that a picture may be obtained in preference to' Aas to and having a combined control for manipulation by an operator stationed within viewing distance oi' said oscilloscope whereby the aperture of said lens and the gain of said amplier may be correlated to produce a signal having an optimum value oi signal to noise ratio and signal components representing maximum depth of focus of said camera.

2. -A television system comprising a. camera having a picture scanning tube, a lens to image a scene on said scanning tube, an adjustable aperture for said lens, power driven means for eifecting adjustment of said aperture, an amplifier connected to amplify the signal output of said camera, an adjustable gain control f or said amplifier, manually operable adjusting means for said gain control, and means adapted for control by said manually operable adjusting means and situated ,adjacent said gainA control adjusting means for controlling the operation of said power driven means.

3.A television system comprising a camera having a picture scanning tube, a lens to image a scene on said scanning tube, an adjustable aperture for said lens, remotely operable means for effectingl adjustment of said aperture, an ampli.

flex' connected to amplify the signal output of said camera, an adjustable gain control for said ampliiier, manually operable adjusting means for said gain control, and means adapted for control bysaid manually operable adjusting means and situated adjacent said gain control adjusting means 'for controlling the operation of said aperture adjusting means.

4. A television system comprising a camera having a picture scanning tube, a lens to image al scene on said scanning tube, iin-'adjustable aperture for said lens, means for effecting adjustment of said aperture, an amplifier connected to amplify the signal output of said camera, an" adjustable gain control for said amplifier, and a combined control for said adjustable gain control and said aperture adjusting means.

5. A television system comprising a camera having a picture scanning tube, a lens to image a scene on said scanning tube, an adjustable aper-l ture 'for said lens, power driven means 4for effect- ,ing adjustment of said aperture, an amplifier connected to amplify the signal output of saidn camera, an adjustable gain control for said am- 1 pline', and a combined control for said adjustable gain control and said power driven apertnre adjusting' means.

. GEORGE-L. BEERB. ff 

